1. Field of the Invention
This invention relates to a method and an apparatus for producing semiconductor devices and, more particularly, to a method and an apparatus for resin-molding semiconductor devices.
2. Description of the Related Art
FIG. 1 illustrates a known resin molding apparatus for resin-molding semiconductor devices. This apparatus has a resin molding section 10 in the center thereof, a loading section 7 and an unloading section 11 which are respectively disposed on the opposite sides of the resin molding section 10. The resin molding section 10, the loading section 7 and the unloading section 11 are covered by dust covers 2, 4 and 6, respectively.
The loading section 7 is provided with a loader 8 for supplying a lead frame and a resin tablet 22 to the resin molding section 10. The loader 8 has a tablet guide portion 24 for receiving the tablet 22 and a slidable stopper 26 for selectively opening and closing the bottom of the tablet guide portion 24.
The resin molding section 10 has a mold 31 and a press 32 for resin-molding semiconductor chips die-bonded to a lead frame which is supplied by the loader 8 of the loading section 7. The mold 31 comprises an upper mold part 28 and a lower mold part 30, and the press 32 acts to press the upper mold part 28 against the lower mold part 30. The lower mold part 30 is provided with a plurality of cavities for receiving semiconductor chips bonded to a lead frame and a pot 34 for receiving the tablet 22. These cavities are connected to the pot 34 through runners.
The unloading section 11 is provided with an unloader 12 for taking out resin-molded semiconductor devices from the resin molding section 10.
The dust cover 4 covering the resin molding section 10 has a first opening 16 on one side wall thereof facing the loading section 7 for allowing the passage of the loader 8, and a second opening 20 on another side wall thereof facing the unloading section 11 for allowing the passage of the unloader 12. A first shutter 24 is provided at the first opening 16 for opening and closing thereof. On the other hand, a second shutter 18 is provided at the second opening 20 for opening and closing thereof.
The operation of the above-described semiconductor resin-molding apparatus is as follows. A lead frame (not shown) to which semiconductor chips are die-bonded is set on the loader 8 of the loading section 7, and a resin tablet 22 is supplied to the tablet guide portion 24 of the loader 8. Then, the first shutter 14 is opened and the loader 8 is introduced into the resin molding section 10 through the opening 16 to set the load frame on the lower mold part 30. In this state, the semiconductor chips bonded to the lead frame are disposed in the cavities. At the same time, the stopper 26 of the tablet guide portion 24 is opened so that the tablet 22 received in the tablet guide portion 24 is dropped into the pot 34 formed in the lower mold part 30. When the loading of the lead frame and the tablet 22 as described above is completed, the loader 8 is returned back to the loading section 7 and the first shutter 14 is closed.
Next, the press 32 is operated to press the upper mold part 28 against the lower mold part 30 so that the mold 31 is closed. Then, the tablet 22 received in the pot 34 is melted by a suitable heating means such as a heater, and is forced out by a plunger or like means and injected through the runners into the cavities, whereby the semiconductor chips are resin-molded.
The resin with which the semiconductor chips and the lead frame are molded is cooled and solidified. Subsequently, the upper mold part 28 is raised by the press 32 and the second shutter 18 is opened. The unloader 12 of the unloading section 11 is then introduced into the resin molding section 10 through the second opening 20 so as to take out the molded semiconductor devices from the lower mold part 30. Each molded semiconductor device, as a product, is thereafter separated from runner portions in the unloading section 11 and placed in a magazine (not shown). Subsequently, the resin burrs adhering to the upper and lower mold parts 28 and 30 are removed by a cleaner (not shown).
During the operation, the dust cover 2 covering the loading section 7 prevents resin powder produced from the tablet 22 for scattering to the outside thereof; the dust cover 4 covering the resin molding section 10 prevents resin burrs produced by resin molding for scattering to the outside thereof; and the dust cover 6 covering the unloading section 11 prevents resin burrs and fine pieces of resin produced by separation of the product and runner portions from scattering to the outside thereof.
It is thus necessary to cover the loading section 7, the resin molding section 10 and the unloading section 11 with the dust covers 2, 4 and 6, respectively, in the known apparatus for producing semiconductor devices. In the loading section 7, semiconductor chips are, however, not yet molded and are exposed to air. Therefore, the resin powder produced from the tablet 22 becomes attached to the semiconductor chips, although the loading section 7 is covered with the dust cover 2. As a result, the properties of the semiconductor chips may be adversely affected.